Portable terminals have gained increasing popularity e.g. due to a significant improvement in their performance. Accordingly, a portable terminal can be used for performing a number of functions that were earlier carried out in a workstation PC or a so-called desktop PC. Such portable terminals include laptop PCs. Nevertheless, even a laptop PC can be inconvenient for some purposes. It can e.g. be uncomfortable to carry a laptop when travelling.
Communication devices, such as Nokia 9210 Communicator, and so-called Palmtop PCs and other pocket-size devices have also been developed, these being used for performing data processing functions and their basic functions making them applicable e.g. as portable terminals. The small size of such devices limits the properties of the devices. For example the memory space of this kind of device is fairly limited in size, when compared e.g. with aforementioned laptop PCs and work station PCs. However, e.g. said Nokia 9210 Communicator communication device can be used for processing the same types of files as computers that are larger in size, within the scope of the memory space and the applications of the communication device that are available for this purpose at each moment of time. At present, the relatively small memory size in prior art solutions prevents storing of large files into a small-size terminal. Also, it is not necessarily possible to use applications that require a lot of memory in this kind of portable terminals. In small-size portable terminals FLASH memory is typically used as auxiliary memory instead of fixed disc. One reason for this is that a FLASH memory unit weighs less compared to hard discs, which enables large storing capacity and which are generally used e.g. in desktop PCs and laptop PCs. Nevertheless, the relatively high costs and slow performance capacity of the FLASH memory limit the quantity of memory that can be implemented by the FLASH memory. Thus, the user should, e.g. when leaving the office, store into the memory of the portable device such files which he/she expects to need outside the office. It is not always possible to predict which files to store into the memory of the portable terminal, wherein it may happen that the file needed by the user does not exist in the memory of the portable device. Moreover, another problem in such joint use of a portable terminal and a fixed workstation is that the user should always update the files amended in the portable terminal also into the memory means of the fixed workstation, or in a local area network environment into the memory means of the local area network, such as a hard disc located on the server. Hence, possible further processing of the file on the fixed workstation does not lose the file changes made in the portable terminal. Further, upon storing a file which is relatively large in view of the total available memory, the free memory space of the portable terminal can subsequently be insufficient for any programs to run, or there is not enough memory for the user to store. Typically, terminals run more slowly the less memory there is available for the user. Portable devices with mobile station functions usually comprise also a phone book feature, wherein it is not desirable that storing files would limit the capacity of the phone book almost to nothingness, or even prevent using the phone book. Also, for the usability of other mobile phone functions (phones, facsimile, text messages, data), a sufficient amount of memory should be available, because these are the most critical functions in terminals such as communication devices. The data processing features of portable terminals are mainly used for data processing, recording of notes, browsing of text files and corresponding features with small memory requirements. Applications designed for this kind of purpose require less memory, but their features are more restricted than e.g. the text processing, spreadsheet and graphics applications developed for desktop PCs.
Such portable communication devices have also been developed that enable the user to store music in compressed form and to listen to the stored music. However, storing a piece of music compressed e.g. into mp3 form requires several megabytes of memory, typically of the order of 4 to 10 Mb for one piece of music. Thus, a large portion of the memory of the portable communication is spent on storing pieces of music and, on the other hand, the number of pieces of music that can be stored into the memory of the portable communication device is limited.
The term file is known as such to an expert in the field. In this specification a file refers e.g. to a group of data that is composed of one or a plurality of data items and is processable in a terminal device as a single unit, wherein at least one common attribute, such as a file name, can be defined for the group of data. Data included in the file can be edited and/or deleted and data can be added. Also, the format of the data can usually be changed. Furthermore, new files can be created and existing files can be deleted. Such files include e.g. text files, such as documents, letters etc. drawn up using a text processing application. Other file types are also known, such as spreadsheet files, data base files, presentation files, graphics files, etc. The files are stored into the memory in binary form and the program processing the file performs the necessary steps for presenting the data contained in the file in a format suitable for the user, e.g. on the display of the terminal.
For mutual updating of data in portable computers and desktop PCs/local area network, an arrangement has been developed to automate the updating. For example for the Windows® operating system, a so-called Briefcase feature has been developed, wherein the user can define one or a plurality of directories that will be updated both in the portable terminal and the desktop PC/local area network. Thus, files amended by a single update command are transferred from one terminal to the other, whereafter both usage environments contain the same files related to the directories in question. Nevertheless, this kind or arrangement is ill-suited for situations in which the storage requirements of the updated directory grows large enough to prevent updating of any files in the portable terminal. A part of the updated files may not be needed by the user, wherein unnecessary memory space is wasted on them. In this case the user should manually remove from the memory of the portable terminal those files that he/she regards redundant. However, the user should remember which files stored in the portable terminal are also stored elsewhere, so that the file can also be processed later if necessary.